With the cost of a decent AGP card, why not buy a cheap motherboard with a pci-ex16 slot? You can get a cheaper graphics card that should outperform or equal a card we can offer anyways.
This is the better deal, mainly because AGP is quite expensive to find nowadays. Another problem is the lack of cards in AGP form, as the 4650 was one of the last from Radeon and I think a few mid classed cards within the 8 series from Nvidia.
You might be able to find a cheap model that's been used, but at the cost of a low-mid card over 100$ you can get a new motherboard that may still support your processor.